Marine seismic surveying employing interpolated multicomponent streamer pressure data

ABSTRACT

It is described a method of interpolating and extrapolating seismic recordings, including the steps of deriving particle velocity related data from seismic recordings obtained by at least one streamer carrying a plurality of multi-component receivers and using the particle velocity related data to replace higher derivatives of pressure data in an expansion series.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/568,803 filed Nov. 7, 2006, now U.S. Pat. No. 8,396,668 issued Mar.12, 2013; which is the U.S. National Stage Application under 35 U.S.C.§371 and claims priority to PCT Application No. PCT/GB2005/001855 filed.May 13, 2005; which claims priority to British Patent Application No. GB0411305.6 filed May 21, 2004; all of which are incorporated herein byreference in their entireties.

The present invention generally relates to methods of interpolating andextrapolating seismic recordings. It particularly relates to suchmethods, where the seismic recordings are obtained using one or moremulti-component towed marine receiver cables or streamers.

BACKGROUND OF THE INVENTION

In the field of seismic exploration, the earth interior is explored byemitting low-frequency, generally from 0 Hz to 200 Hz, acoustic wavesgenerated by seismic sources. Refractions or reflections of the emittedwaves by features in the subsurface are recorded by seismic receivers.The receiver recordings are digitized for processing. The processing ofthe digitized seismic data is an evolved technology including varioussub-processes such as noise removal and corrections to determine thelocation and geometry of the features which perturbed the emitted waveto cause reflection or refraction. The result of the processing is anacoustic map of the earth's interior, which in turn can be exploited toidentify, for example, hydrocarbon reservoirs or monitor changes in suchreservoirs.

Seismic surveys are performed on land, in transition zones and in amarine environment. In the marine environment, surveys include sourcesand receiver cables (streamers) towed in the body of water and oceanbottom surveys in which at least one of sources or receivers are locatedat seafloor. Seismic sources and/or receivers can also be placed intoboreholes.

The known seismic sources include impulse sources, such as explosivesand airguns, and vibratory sources which emit waves with a morecontrollable amplitude and frequency spectrum. The existing receiversfall broadly speaking into two categories termed “geophones” and“hydrophones,” respectively. Hydrophones record pressure changes,whereas geophones respond to particle velocity or acceleration.Geophones can record waves in up to three spatial directions and areaccordingly referred to as 1C, 2C or 3C sensors. A 4C seismic sensorwould be a combination of a 3C geophone with a hydrophone. Both types ofreceivers can be deployed as cables with the cable providing a structurefor mounting receivers and signal transmission to a base station. Suchcables fall into two distinct categories: one being so-calledocean-bottom cables which maintain contact with the sea-floor, while thesecond category is known as streamers which are towed through the waterwithout touching the sea-floor.

Presently, the seismic industry is in the process of developingmulti-component cables or streamers. Multicomponent streamers include aplurality of receivers that enable the detection of pressure andparticle velocity or time derivatives thereof. In so-called dual sensortowed streamers, the streamer carries a combination of pressure sensorsand velocity sensors. The pressure sensor is typically a hydrophone, andthe motion or velocity sensors are geophones or accelerometers. In theU.S. Pat. No. 6,512,980, a streamer is described carrying pairs ofpressure sensors and motion sensors combined with a third sensor, anoise reference sensor. The noise reference sensor is described as avariant of the prior art pressure sensor.

In the United Kingdom patent application GB 0402012.9, there is proposeda streamer having a plurality of compact clusters of hydrophones. Thestreamer is adapted to provide gradient measurements of pressure, whichin turn can be readily transformed into particle velocity data.

The main motivation for developing multi-component streamers has been todecompose the recorded data into its up- and down-going components,i.e., to free the data of “ghosts” caused by reflection at the seasurface. In this memo we introduce a new application area formulti-component streamers.

On the other hand, the seismic industry has since long experienced theneed to interpolate or extrapolate trace recordings into areas void ofreceivers. Normally the wavefield and/or its derivatives are only knownat a number of discrete locations. However, in practice it is oftendesirable to extend the knowledge of the wavefield to other points usinginterpolation, extrapolation or a combination of extrapolation andinterpolation, sometimes known as intrapolation. Such techniques areapplied, for example, to determine pressure data along the streamer,away from a streamer, at near-source offsets, or between two adjacentstreamers.

In the light of the above prior art, it is seen as an object of thepresent invention to provide improved methods of interpolating andextrapolating seismic recordings.

SUMMARY OF THE INVENTION

In an aspect of the invention the measured data from a multi-componentstreamer are used to derive a filter which interpolates or extrapolatespressure data away from the location of the streamer.

The filter is preferably based on an expansion series of the pressuredata.

An expansion series is generally defined as a representation of afunction or data set by means of a sum of increasing higher derivativesof the function or data set at a point or the space surrounding a point.One of the most used expansion series is the Taylor series. WhereasTaylor series are generally not suitable for extrapolating oscillatoryfunctions over great distances, the invention is based on therealization that in seismic applications the waves arrive at thereceivers with near vertical incidence.

For certain applications, in particular for intrapolation between knownpoints of the data set, it is a preferred variant of the presentinvention to use a Taylor series with modified weighting, morepreferably weighting known as barycentric or triangular weighting.

Though expansion series have been proposed in seismic theory, they wereseverely restricted in real application because such expansions lead tocross-line terms which are difficult to evaluate. Lack of accurateparticle velocity caused further problems: Without such data, the errorsmade by intra- and extrapolation render the results unreliable. It hasnow been found that multi-component streamers are capable of providingsufficiently accurate particle velocity related data either directly orindirectly.

In a preferred embodiment of the invention, first-order cross-linederivatives of data in the filter or expansion series are substituted byin-line derivatives. In a more preferred embodiment of the invention,first-order and second-order cross-line derivatives of data in thefilter or expansion series are substituted by in-line derivatives.

In a preferred embodiment the expansion series is accurate to afirst-order, more preferably to the second-order expansion term.Clearly, it is desirable to extend the series into the highest orderpermitted by the available computing power. However, the terms involvemore and more complex derivatives of the measured data. Hence, such anextension is preferably limited to the term which can be replaced orexpressed in terms of accurately measured data.

In a preferred embodiment functions, preferably linear functions ofparticle velocity related data and in-line pressure data are used toreplace higher cross-line derivatives of pressure data in the expansionseries.

Herein, the terms “in-line” and “cross-line” are used in theirconventional meaning in the seismic industry, hence, as the directionalong the main streamer axis and the direction perpendicular to it,respectively. The derivatives used are preferably spatial derivativesand more preferable spatial derivatives in in-line direction.

The methods described herein can be used for many applications,including but not limited to extrapolating into a direction away from astreamer, intrapolating into a space between two streamers, even in casethat one of the streamers is not a multi-component streamer,intrapolating into a direction along a streamer, or intrapolating into aspace closer to a seismic source.

It is advantageous to be capable of intrapolating into a direction alonga streamer to maximize or otherwise optimize receiver spacing in thestreamer.

Interpolation of marine seismic recordings is fundamental to processingof 3D seismic data. Applications include imaging and multipleelimination (short source-receiver offsets, cross-line receiverlocations, etc.). The present invention can allow for better 3Dsolutions to, for instance, imaging and multiple removal problems aswell as significantly increasing efficiency of marine seismicoperations.

In addition, time-lapse in an important application area whereinterpolation/extrapolation of actual receiver locations to those in thelegacy data can be critical to isolate the time-lapse response fromnoise introduced by deviations from the ideal time-lapse survey.

The methods of the present invention can also be beneficial in multipleelimination and imaging as well as in time-lapse applications or otherapplication where a regularization of data location has an advantage.

The methods of this invention can also be used tointerpolate/extrapolate into vertical (z) direction.

These and other aspects of the invention will be apparent from thefollowing detailed description of non-limitative examples and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and 1B illustrate a typical marine seismic survey with towedstreamers;

FIG. 2 is a diagram illustrating steps in accordance with an example ofthe invention;

FIGS. 3A-3C compare the performance of interpolations with increasingorder in accordance with examples of the invention at one dB value(−26); and

FIGS. 4A-4C compare the performance of interpolations with increasingorder in accordance with examples of the invention at a range of dBvalues.

DETAILED DESCRIPTION

A typical marine seismic acquisition is illustrated in FIGS. 1A and 1B,which show a schematic top and side view on a marine seismic survey.Four instrumented cables or streamers 10 are towed by a ship 11. A frontnetwork 12 and similar tail network (not shown) is used to connect thevessel and the streamers. Embedded in the front network are seismicsources 13, typically an array of airguns. Each streamer 10 is typicallyassembled from many receiver holder segments that are coupled to make upthe streamer. Between segments, the streamers carry controllabledeflectors 111 (often referred to as vanes or “birds”) and other aidsfor steering the streamer along a desired trajectory in a body of water.

The accurate positioning of modem streamers is controlled by a satellitebased positioning system, such as GPS or differential GPS, with GPSreceivers at the front and tail of the streamer. In addition to GPSbased positioning, it is known to monitor the relative positions ofstreamers and sections of streamers through a network of sonictransceivers 112 that transmit and receive acoustic or sonar signals.

The main purpose of a streamer 10 is to carry a large number of seismicreceivers 101 which are distributed along its length. In FIG. 1 thereceivers are schematically depicted as marked boxes. Each receiver canbe either two or more hydrophones arranged in a plane orthogonal to thestreamer axis as described in the United Kingdom patent application no.GB 0402012.9 filed on Jan. 30, 2004. Alternatively, each receiver may bea dual sensor as described in U.S. Pat. No. 6,512,980.

During a survey, the sources 13 are fired at intervals and the receivers101 “listen” within a frequency and time window for acoustic signalssuch as reflected and/or refracted signals that are caused by seismicfeatures in path of the emitted wavefield. As a result of such a survey,a set of pressure data P(x,y,t) and, by making use of themulti-component capability of the streamer, a set of velocity relateddata V(x,y,t) are obtained at locations x,y and times t. The velocity isa vector with for example components in x, y and z.

The coordinates are Cartesian coordinates with x as in-line direction,which is a direction parallel to the main axis of the streamer, and y ascross-line direction perpendicular to the streamer axis and parallel tothe (ideal) sea surface or plane in which the parallel streamers aretowed. And the zdirection is taken to be vertical and orthogonal to xand y.

Applying the well-known Taylor's theorem, an analytic wavefield can beextrapolated away from a location where the wavefield and itsderivatives are known:

$\begin{matrix}{{P\left( {{x + {\Delta \; x}},{y + {\Delta \; y}}} \right)} = {{P\left( {x,y} \right)} + \left\lbrack {{\Delta \; x\; {\partial_{x}{P\left( {x,y} \right)}}} + {\Delta \; y{\partial_{y}{P\left( {x,y} \right)}}}} \right\rbrack + {\frac{1}{2!}\left\lbrack {{\left( {\Delta \; x} \right)^{2}{\partial_{xx}{P\left( {x,y} \right)}}} + {2\Delta \; x\; \Delta \; y{\partial_{xy}{P\left( {x,y} \right)}}} + {\left( {\Delta \; y} \right)^{2}{\partial_{yy}{P\left( {x,y} \right)}}}} \right\rbrack} + {\frac{1}{3!}\begin{bmatrix}{{\left( {\Delta \; x} \right)^{3}{\partial_{xxx}{P\left( {x,y} \right)}}} + {3\left( {\Delta \; x} \right)^{2}\Delta \; y{\partial_{xxy}{P\left( {x,y} \right)}}} +} \\{{3\Delta \; {x\left( {\Delta \; y} \right)}^{2}{\partial_{xyy}{P\left( {x,y} \right)}}} + {\left( {\Delta \; y} \right)^{3}{\partial_{yyy}{P\left( {x,y} \right)}}}}\end{bmatrix}} + {o\left( \Delta^{4} \right)}}} & \lbrack 1\rbrack\end{matrix}$

Where +o(Δ^(n)) indicates the order of terms neglected in the Taylorexpansion (4 in equation [1]), and the operator ∂_(x) denotes a spatialpartial derivative—in this instance with respect to the x-direction. TheTaylor series is infinite and is valid for extrapolation any distanceaway from the location where the wavefield and its derivatives areknown.

The range of the extrapolation is limited by truncating the Taylorseries. Weights for extrapolation/interpolation can also be derived inother ways than through Taylor expansions. As an example in oneembodiment of the current invention we derive numerically optimizedweights to yield optimal results of interpolated/extrapolated overcertain frequency bands and arrival angles (i.e., wavenumbers). In thefollowing examples pressure data are extrapolated.

An application of the general equation of motion yields

∂_(x) P(x,y)=ρ{dot over (V)} _(x)(x,y)  [2]

and

∂_(y) P(x,y)=ρ{dot over (V)} _(y)(x,y),  [3]

where {dot over (V)}_(x), {dot over (V)}_(y) denote a time derivativesof V_(x), and V_(y), respectively, and ρ is the density of water. Usingequation [3] to replace the cross-line derivative of the pressure, allthe terms required for the first-order accurate Taylor expansion ofpressure away from the multi-component streamer are available:

P(x+Δx,y+Δy)=P(x,y)+[Δx∂ _(x) P(x,y)+Δyρ{dot over (V)}_(y)(x,y)]+O(Δ²).  [4]

In equation [4] the option exists of expressing in-line derivatives withrespect to pressure in terms of derivatives of in-line component ofparticle velocity through equation [2]. However, in the examples thein-line derivatives of pressure are used throughout. A variant ofequation [4] can be applied to expansions into z-direction.

The second-order cross-line derivative of pressure from a 10multi-component streamer towed in the vicinity of the sea surface (e.g.,at 6m depth) can be expressed as:

$\begin{matrix}{{\partial_{yy}{P\left( {x,y} \right)}} = {{\frac{3}{1 + {\frac{2}{15}k^{2}h^{2}}}\begin{bmatrix}{{\frac{k\; {\cot ({kh})}}{h}{P\left( {x,y} \right)}} -} \\{\frac{{\omega}\; \rho}{h}{V_{z}\left( {x,y} \right)}}\end{bmatrix}} - {\partial_{xx}{P\left( {x,y} \right)}} + {O(h)}}} & \lbrack 5\rbrack\end{matrix}$

Equation [5] is expressed in the space-frequency domain, h denotes theinstantaneous depth of each recording element as a function of time andspace and k=ω/c is the wavenumber where ω is the angular frequency and cis the velocity in water. In order to be applicable for a time-variantrough sea, a space-time implementation using compact filters of equation[5] is necessary. This can be done successfully either by approximatingthe k dependent terms by truncated Taylor expansions (equivalent totime-derivatives in the time domain) or by overlapping triangularwindows where the wave-height is considered constant within each window.

Combining equations [1], [3] and [5] the Taylor expansion of pressureaway from the multi-component streamer can be written as accurate up tothe second order:

$\begin{matrix}{{P\left( {{x + {\Delta \; x}},{y + {\Delta \; y}}} \right)} = {{P\left( {x,y} \right)} + \left\lbrack {{\Delta \; x\; {\partial_{x}{P\left( {x,y} \right)}}} + {\Delta \; y\; \rho \; {{\overset{.}{V}}_{y}\left( {x,y} \right)}}} \right\rbrack + {\frac{1}{2}\left\lbrack {{\left( {\Delta \; x} \right)^{2}{\partial_{xx}{P\left( {x,y} \right)}}} + {2\Delta \; x\; \Delta \; y\; \rho \; {\partial_{x}{{\overset{.}{V}}_{y}\left( {x,y} \right)}}}} \right\rbrack} + {\frac{\left( {\Delta \; y} \right)^{2}}{2}\left\lbrack {{\frac{3}{1 + {\frac{2}{15}k^{2}h^{2}}}\begin{bmatrix}{{\frac{k\; {\cot ({kh})}}{h}{P\left( {x,y} \right)}} -} \\{\frac{\; \omega \; \rho}{h}{V_{z}\left( {x,y} \right)}}\end{bmatrix}} - {\partial_{xx}{P\left( {x,y} \right)}}} \right\rbrack} + {o\left( \Delta^{3} \right)}}} & \lbrack 6\rbrack\end{matrix}$

Having derived expressions of the first- and second-order Taylorexpansion in terms of measurable data, these expressions can be appliedas filter to various problems of interest to seismic exploration anddata analysis. A practical filter may approximate analytical expressionssuch as derivatives by their corresponding finite differenceapproximations.

As shown in FIG. 2, the applications for filters in accordance with theinvention include generally the steps of obtaining the multi-componentdata using a multi-component streamer (Step 21), using an expansionequation with cross-line terms replaced as described above (Step 22) andusing suitable computing devices to determine the inter- or extrapolateddata (Step 23).

The first of such problems relates to the interpolation andintrapolation of pressure data in the direction along a streamer so asto derive values of the dataset at points between the location ofreceivers.

The problem of interpolating a wavefield between two points where thevalue of the wavefield and some of its derivatives are known iswell-known in 1D and is solved by fitting Hermite polynomials to thedata.

The multi-component streamer will have some redundancy in in-linemeasurements if both P and Vx are recorded. This redundancy may beexploited to attenuate noise in a multi-component streamer. For the casewhere there are recordings of both P and V_(x) and in order to suppressnoise on P by means of filtering the maximum required sensor spacing canbe relaxed, if a sufficiently dense grid of data values can be generatedthrough interpolation. As the noise on the geophone components will bespatially aliased, this method may require a model for predicting thenoise on the geophone components once it is known on the pressurecomponents.

Hermite polynomials allow us to interpolate P data from neighboring Pand V_(X) recordings between x=x₀ and x=x₁ even though the slowestpropagating noise mode may be 30 spatially aliased on the P recordingsthemselves:

P(x,y ₀)=P(x ₀ ,y ₀)(2s ³−3s ²+1)+P(x ₁ ,y ₀)(−2s ³+3s ²)+ρ{dot over(V)} _(x)(x ₀ ,y ₀)(s ³−2s ² +s)+ρ{dot over (V)} _(x)(x ₁ ,y ₀)(s ³ −s²)  [7]

where the Hermite polynoms are written as function of

$s = {\frac{\left( {x - x_{0}} \right)}{\left( {x_{1} - x_{0}} \right)}.}$

A second application is the extrapolation away from a streamer.

To extrapolate pressure data away from a multi-component steamer, butnot into the direction of another multi-components streamer, a 1DHermite interpolation can be applied along the streamer to the pointalong the streamer that has the shortest distance to the point to whichthe data is to be extrapolated. The interpolation along the streamer canbe performed to an arbitrary degree of accuracy by computing derivativesin the streamer direction of the different terms needed for the Taylorextrapolation (equation [4] or equation [6]) with spectral accuracy,provided that the required terms are not spatially aliased.

The Hermite interpolation, however, cannot be arbitrarily extended as byincluding ever higher-order derivatives more noise will be amplified.

The third problem relates to the interpolation and intrapolation ofpressure data between two multi-component streamers.

A Hermite interpolation can likely not be used cross-line in between thestreamers as the terms for a subsequent Taylor extrapolation probablyare aliased. Instead, one needs to derive a modified form of the Taylorintrapolation formulae to constrain the extrapolated wavefield betweenthe neighboring streamers for this special case.

If the wavefield and its derivatives are known at the corners of atriangle and one would like to interpolate the wavefield to a point inthe interior of the triangle, a first possible method is to use 2DTaylor expansion for each of the three points (equation [1j) and thenlinearly interpolate or weight the three values according to theirbarycentric weights. However, it has been shown that this will result inan intrapolated wavefield with one degree of accuracy less than what canbe achieved if the Taylor expansion coefficients are modified slightlysuch that the interpolants are forced to fit the data at all corners ofthe triangle and not only one at a time. An example of the modifiedTaylor expansion can be found for example in a recent thesis by D.Kraaijpoel, “Seismic ray fields and ray field maps: theory andalgorithms. Utrecht University (2003).

Hence, to intrapolate the wavefield between two multicomponent streamersthe domain of receiver locations is triangulated such that each point inbetween the two streamers falls within a triangle with a receiverlocation at each corner. The wavefield is then extrapolated from each ofthe three recording locations to the interior point using the modifiedTaylor expansion. The data are then averaged using barycentric(triangular) weighting. The first- and second-order modified Taylorexpansions of pressure P are (see for example Kraaijpoel, 2003):

{tilde over (P)}(x+Δx,y+Δy)=P(x,y)+½[Δx∂ _(x) P(x,y)+Δyρ{dot over (V)}_(y)(x,y)]+O(Δ²),[8]

for the first-order expansion and as second-order expansion:

$\begin{matrix}{{\overset{\sim}{P}\left( {{x + {\Delta \; x}},{y + {\Delta \; y}}} \right)} = {{P\left( {x,y} \right)} + {\frac{2}{3}\left\lbrack {{\Delta \; x{\partial_{x}{P\left( {x,y} \right)}}} + {\Delta \; y\; \rho \; {{\overset{.}{V}}_{y}\left( {x,y} \right)}}} \right\rbrack} + {\frac{1}{6}\left\lbrack {{\left( {\Delta \; x} \right)^{2}{\partial_{xx}{P\left( {x,y} \right)}}} + {2\Delta \; x\; \Delta \; y\; \rho \; {\partial_{x}{{\overset{.}{V}}_{y}\left( {x,y} \right)}}}} \right\rbrack} + {\frac{\left( {\Delta \; y} \right)^{2}}{6}\begin{bmatrix}{{\frac{3}{1 + {\frac{2}{15}k^{2}h^{2}}}\begin{bmatrix}{{\frac{k\; {\cot ({kh})}}{h}{P\left( {x,y} \right)}} -} \\{\frac{\; \omega \; \rho}{h}{V_{z}\left( {x,y} \right)}}\end{bmatrix}} -} \\{\partial_{xx}{P\left( {x,y} \right)}}\end{bmatrix}} + {{o\left( \Delta^{3} \right)}.}}} & \lbrack 9\rbrack\end{matrix}$

There are different coefficients in front of the terms in equations [8]and [9] compared to the traditional Taylor expansions [equations (4) and(6)]. The equations [8] and [9] are best used when interpolating data in2D and not for extrapolation. The triangularization can also be usedwhen intrapolating between streamers on highly degenerated triangles.One side of such triangles is formed by the receiver spacing while theother two are determined by the much larger distance between streamers.Thus the above equations can be applied in the limit of Δx->0.

A fourth problem to which methods in accordance with the presentinvention can be applied is the intrapolation of pressure data at nearsource offsets.

This is a special case particularly important for applications in thefield of multiple suppression. Generally, a survey obtains data frommultiple adjacent streamers as shown in FIG. 1. But no data areavailable in the region closer to the source. However, at the sourcelocation symmetry conditions can be used in the interpolation such thatthe pressure data are symmetric across the location of the source. Inother words, a Taylor expansion of the wavefield away from the sourcelocation will only contain even terms which are symmetric (pressure,second derivatives of pressure, etc.), but no odd terms which areanti-symmetric. The argument is correct for the direct wave and for thecase of a one-dimensional (1D) model of the Earth but breaks down withvariations in the subsurface. However, the symmetry is likely to be astrong additional constraint for extrapolation to near offsets. If thenear-field source signature is known (e.g., by using the CMS™ technologyof Western-Geco), then such information may be added to constrain theinterpolation of the direct arrival.

Finally, another special case is that of a multi-component streamertowed parallel to a conventional streamer recording P data only (P andall in-line spatial derivatives are known). Also for this case amodified form of the Taylor intrapolation formulae as above to constrainthe extrapolation is likely to benefit from the fact-that the pressurewavefield and its in-line derivatives are known along the conventionalstreamer.

To numerically test the performance of the above-described methods, anoise-free ray-based 3D synthetics was generated using a 50 Hzmonochromatic source. The source was placed at the origin at 6m depthbelow the sea surface. Recordings were made at 6m below the sea surface.A primary reflection was simulated from a reflector with a reflectioncoefficient of 1. The medium between source, receivers and the reflectorwas taken to be homogeneous with a velocity of 1500 m/s. The sea surfacewas modeled as a flat reflector with a reflection coefficient of −1. Thereceiver-side ghosts were included in the synthetics.

The plots of FIGS. 3A to 3C illustrate the error between the correctresponse and the intrapolated response in case of the reflector beinglocated at a depth of 2500m below the source and a cross-line dip of 10degrees. The dip results in a wave arriving at 20 degrees angle at thereceivers.

The −26 db contour is shown as lines 31. The ordinate shows the inlinedistance from the source location, while the abscissa is the cross-lineoffset or distance with a streamer located at the left border and secondstreamer located at the right border of the plot. The distance betweenthe two streamers is set to be 100 m.

The plot of FIG. 3A is the intrapolation using pressure data only, hencethe data available from two conventional streamers. In FIG. 3B, afirst-order intrapolation using equation [8] is shown and in FIG. 3 thesecond-order intrapolation of equation [9] is used. With increasingorder of interpolation, accurate data can be calculated in increasingdistance from the location of the receivers. In FIG. 3C the −26 dBcontour line 31, is split into several regions.

Full colored plots of the FIGS. 3A-3C are added as FIGS. 4A to 4C.

Each of the following applications is hereby incorporated by referencefor all purposes as if set forth verbatim herein:

-   -   U.S. application Ser. No. 11/568,803, entitled, “Marine Seismic        Surveying Employing Interpolated Multicomponent Streamer        Pressure Data,” and filed Nov. 7, 2006, in the name of the        inventor Johan Olaf Anders Robertsson;    -   International Application No. PCT/G92005/001855, entitled,        “Interpolation and Extrapolation Method for Seismic Recordings,”        filed May 13, 2005, under the Patent Cooperation Treaty and        naming Johan Olaf Anders Robertsson as inventor;    -   GB 0411305.6, entitled, “Interpolation and Extrapolation Method        for Seismic Recordings,” and filed May 21, 2004, naming Johan        Olaf Anders Robertsson as inventor.        Each of these applications is commonly assigned herewith.

While the invention has been described in conjunction with the exemplaryembodiments described above, many equivalent modifications andvariations will be apparent to those skilled in the art when given thisdisclosure. Accordingly, the exemplary embodiments of the invention setforth above are considered to be illustrative and not limiting. Variouschanges to the described embodiments may be made without departing fromthe spirit and scope of the invention.

1. A method of interpolating and/or extrapolating seismic recordings,comprising: obtaining multi-component seismic data from at least onestreamer carrying a plurality of multi-component receivers; usingspatial derivatives obtained from the multi-component seismic data in aninterpolating and/or extrapolating filter, wherein the filter comprisesone or more functions of the spatial derivatives associated with atleast one direction defined in relation to the at least one streamer;and applying the filter to the multi-component seismic data to yield newdata associated with a location that has not been measured by theplurality of receivers in the seismic recordings.
 2. The method of claim1, wherein the spatial derivatives comprise pressure gradient values,particle velocities or derivatives thereof.
 3. The method of claim 1,wherein the spatial derivatives are finite difference approximations. 4.The method of claim 1, wherein the functions of the spatial derivativesassociated with the at least one direction are replaced by functions ofspatial derivatives associated with a different direction.
 5. The methodof claim 4, wherein the different direction comprises a directionsubstantially parallel to a plane in which streamers in a seismic spreadare towed.
 6. The method of claim 4, wherein the at least one directionis the cross-line direction between the at least one streamer andanother streamer, and wherein the different direction is the in-linedirection along the at least one streamer.
 7. The method of claim 1,wherein the at least one direction comprises a direction vertical to theat least one the streamer.
 8. The method of claim 1, wherein the atleast one direction comprises a direction substantially perpendicular tothe main axis of the at least one streamer.
 9. The method of claim 1,wherein the at least one direction comprises a direction substantiallyparallel to the sea surface.
 10. The method of claim 1, wherein the atleast one direction comprises a direction substantially parallel to themain axis of a streamer.
 11. The method of claim 1, wherein the at leastone direction comprises a direction along the at least one streamer. 12.The method of claim 1, wherein the spatial derivatives are derived fromthe multi-component seismic data.
 13. A method of interpolating and/orextrapolating seismic recordings, comprising: obtaining multi-componentseismic data from at least one streamer carrying a plurality ofmulti-component receivers; and using cross-line spatial derivativesobtained or derived from the multi-component seismic data in aninterpolating and/or extrapolating filter for the multi-componentseismic data, wherein the cross-line spatial derivatives are replaced byfunctions of in-line spatial derivatives.
 14. The method of claim 13,wherein the cross-line or in-line spatial derivatives comprise pressuregradient values, particle velocities or derivatives thereof.
 15. Themethod of claim 13, wherein the multi-component seismic data comprisespressure data and/or particle motion data.
 16. The method of claim 13,wherein the in-line spatial derivatives describe a pressure wavefieldmeasured along the at least one streamer.